Conventionally, in a car, in wiring a wire harness by spanning the wire harness between a car-body panel 1 and a trunk lid 2 which is opened or closed, as shown in FIG. 4, a grommet 3 is externally mounted on the wire harness for waterproofness and dust resistance of the wire harness. The present applicant proposed such a grommet 3, as disclosed in Japanese Patent Application Laid-Open No. 2001-258129 (patent document 1). The grommet 3 is composed of the bellows-like cylindrical part 3a through which the wire harness is inserted and the locking cylindrical part 3b, continuous with the bellows-like cylindrical part 3a, which is formed at both ends of the bellows-like cylindrical part 3a. The locking cylindrical part 3b is inserted into and locked to the through-holes formed through the car-body panel 1 and the trunk lid 2.
As shown in FIG. 5, the bellows-like cylindrical part 3a of the grommet 3 through which electric wires have been inserted is bent in the shape of U, when the trunk lid 2 is closed. The number of the electric wires to be inserted through the grommet 3 is different according to the kind and grade of a car. When the number of the electric wires is large, the electric wires have a high rigidity.
Thus as shown in FIG. 5(A), the bellows-like cylindrical part 3a gently curves in the shape of U. On the other hand, when the number of the electric wires is small, the electric wires have a low rigidity. Thus as shown in FIG. 5(B), the bellows-like cylindrical part 3a that has been curved in the shape of U bends greatly at a curved portion. Therefore there is a case in which the bent portion has a small curvature R. When the trunk lid 2 is opened, the bellows-like cylindrical part 3a of the grommet 3 through which the wire harness has been inserted becomes straight. Owing to opening and closing the trunk lid 2, the bellows-like cylindrical part 3a repeats a bent state in which the bellows-like cylindrical part 3a has a small curvature R and a straight state. As a result, the electric wires inserted through the grommet 3 undergo metal fatigue and are damaged. In this case, there is a fear that the electric wires are broken. There is also a fear that the grommet 3 is damaged.
Patent document 1: Japanese Patent Application Laid-Open No. 2001-258129